This application relates to a chair-specific adjustment device. Many devices are known today that control a specific inclination between a chair or an armchair's seat and backrest.
For example, German Patent No. DE 4,318,516 A1 (hereinafter “the '516 patent”) is known, wherein a device is described that changes the reciprocal position between a chair's two mobile components. This device is comprised of a bolt engaging a gear adjacent to the body of a chair to lock it in the various different positions. The device can be defined as bi-stable, in the sense that it enables two different stable positions for the bolt. The bolt's movements are controlled by a device lodged in a container, the bolt is adjacent to a rod to which a pair of misaligned spindles are attached. A first spring acts between the rod and the container while a second spring, stronger than the previous one, acts between the container and the enlarged head of the pin.
The device of the '516 patent is activated by the user rotating a lever or cam, which presses on the pin's head; this rotation is applied on an axis perpendicular to the pin's; the lever is a precise, though not discreet, length in order to allow the user to apply, further to the effort applied in order to obtain the rotation, a sufficient axial push on the head, which becomes a drawback because of the resulting spatial arrangement imposed by the various components.
The solution described by the '516 patent presents many other drawbacks, as well as the overall structural complexity and the volume occupied by the single components, such as the need to apply a certain rotation strength on the lever to achieve the desired shifting in any case; this lever is also not particularly easy to activate, since the rotation force applied to the lever needs to translate into an axial push for the pin. Finally, the mechanical interaction between the bolt and the gear wheel is likely to get stuck.
Another example includes Italian patent for utility Model No. 225116, filed on Jul. 12, 1991 (hereinafter “the'116 patent”), which relates to an oscillating group for chairs with locking mechanism for various positions, where a device is described that interacts with a lever in order to lock it in different positions or release it, to allow or impede the oscillations of the oscillating support respectively, and the seating elements, with respect to the box body, along with it.
The device of the '116 patent is comprised of a maneuver lever that can rotate on its own axis, radially associated to a stiff tie-beam, with an end connected to said lever, and a locking element connected to the other end of the tie-beam. The locking element also rotates on its own vertical axis and moves towards and away from the lever arm, further to the rotation of the maneuver lever. There are springs that make the device basically bi-stable, in the sense that further to ensuing activations of the maneuver lever, it can ensure two corresponding stable positions.
This device also shows some drawbacks. It is made up by many components which are variably arranged in their seating and interconnections, thus making the production and assembly of the device costly. Also, the activation of the locking element is caused by actuating the lever, but this transmits the motion through the interposition of the stiff tie-beam, which can come loose or become deformed as a result of the applied forces. Additionally, the joint of the locking element creates further drawbacks, owed to the possible activation problems caused both to possible seizures or obstacles to the fluidity between elements, and to the force that needs to be exerted in order to overcome both the resistance of a spring and the friction between the lever arm and the locking element, a friction that becomes greater the longer the user is seated during the maneuver and therefore increases the coupling between the lever arm and the locking element.
Also known is the Italian patent for Industrial Invention, Application Publication No. ITMI20050751, filed on Apr. 27, 2005, illustrating an adjustment mechanism for the inclining of backrests in chairs and armchairs, especially office chairs, where backrest inclination controls are involved as well as spring mechanisms to bring the backrest towards its minimum inclination position.
These backrest inclination controls include at least one step limit group, one of the steps' tasks being to interfere with an element linked to the backrest during its reclining movements, as the limit group can be shifted into various discreet positions or the element linked to the backrest, in order to limit said element between the minimum reclining position and an interference position linked to the backrest with the chosen step in the group.
This solution also shows some drawbacks as the support for the backrest is connected to a lever which, as it needs to move longitudinally to the mechanism is subject to friction or getting stuck or deformations that could prevent its correct operation; also, the activation of the lever through the cam is not smooth, since the cam has to receive a rotary movement which, combined with the lever oscillation, must lead the pin to interact with one of the group steps, which is fixed, and so that could lead to further catching and incorrect positions.
Also, in the event of using a pinion, the latter needs to engage a rack to obtain a longitudinal movement that will make one of the steps available for the support extremity: in this case also there will be frictions between the various surfaces that can make the components' movement clumsy.
European Patent No. EP 0902634 (hereinafter “the '634 patent”) is also known, claiming an Italian priority for the utility Model No. 242153, filed on Jan. 8, 1996, with Italian Patent Application No. VE96U000001, where a generic inclination adjustment device for chairs and armchairs is illustrated, characterized for its inclusion of a bolt that is part of the locking system and is fixed to one of the two parts of the seating support, a number of holes on the other side of the seating support in positions that can be engaged by the bolt and which correspond to the different reciprocal inclinations between the two parts of said support, an axial control stem of said bolt, an axially unstable device for the control of said stem, a couple of preloaded springs interplaced between said stem and said bi-stable device and a control button of said bi-stable device.
The solution of the '634 patent also presents many drawbacks: firstly, the device is activated with a button, which is usually placed next to a handle below the chair; this button isn't easy to reach. Also, the bolt is placed remotely compared to the button, so the stem is needed, which is lodged in its own sheath that lies between the bolt itself and the button needed for its activation. The presence of the sheath can also lead to a less than optimal activation of the bolt, as the stem cannot flow optimally when the button is activated within its sheath or in any case lead to a deformation of the same, which makes the push towards the bolt useless. Finally, in the mentioned technique, the positioning of the various components always appears discreet and so the user can choose between two positions that do not exactly correspond to the one they sought, but only come close.